The use of modems for data communication over a cellular network is becoming more and more popular. As people use personal digital systems (PDA), portable laptops, and other systems, they desire to send data from these systems across the cellular network. One way of implementing these systems is to use a modem unit associated with each of these host processor units. When a company owns a large number of mobile units, it can be difficult to keep track of the status of these mobile units. For this reason it is desired for a user at a central location to obtain status information for a number of mobile units in the field.